Preparation And Characterization Of CuFeS₂ Photoelectric Material

Chalcopyrite compounds such as CuAlS₂,CuInSe₂,CuGaSe₂,CuInS₂ and CuFeS₂ are all representative of ternary chalcogenides with a broad band distribution from 0.6eV to 3.5eV.As a photovoltaic material,CuFeS₂ is a ternary I–III–VI₂ compound semiconductor with the crystal structure of chalcopyrite and sphalerite.It has the advantages of low price,abundant reserves and non-toxicity compared with other chalcogenides.In recent years,the applications of CuFeS₂ films,nanowires,nanorods,spherical particles and nanocrystals in solar photovoltaic panels,thermoelectric devices and spintronic devices have been widely concerned by scientists.CuFeSe₂belongs to the I-III-VI₂ compound semiconductor and is a semiconductor material with extremely narrow band gap,which has potential application value in optoelectronic materials.The methods of preparing solar thin film batteries are mainly electrochemical deposition,sputtering,thermal evaporation,thermal spraying and hydrothermal co-reduction.In this paper,CuFeS₂ and CuFeSe₂ powders and thin film materials were prepared by hydrothermal method and hydrothermal chemical co-reduction method.The main contents of the study are as follows:（1）The CuFeS₂ powders were synthesized by simple hydrothermal co-reduction method,the effects of different heat treatment conditions and different sulfur source types on the preparation of CuFeS₂ phase were systematically studied.With CuCl₂·2H₂O and FeCl₃·6H₂O as raw materials,the effects of different sulfur sources（S,H₂NCSNH₂,Na₂S₂O₃·5H₂O）on the phase of CuFeS₂ were discussed.It was found that when sulfur source was sulfur powder,the sample crystallized well and had no impurity formation.With the reaction temperature extending to220℃,the diffraction peak intensity is obviously improved.The effect of heat treatment temperature and time on the morphology of CuFeS₂ powder was found with the change of heat treatment time and temperature.（2）Two systems,copper chloride（CuCl₂·2H₂O）,iron trichloride（FeCl₃·6H₂O）,sodium thiosulfate（Na₂S₂O₃·5H₂O）and copper sulfate（CuSO₄·5H₂O）,ferrous sulfate（FeSO₄·7H₂O）and sodium thiosulfate（Na₂S₂O₃·5H₂O）,were selected.CuFeS₂ thin films were prepared by hydrothermal chemical co-reduction method.It was found that when the heat treatment temperature and heat treatment time were 180℃and 10 h,the film crystallized best and no impurities were formed.The morphology of the film was analyzed by SEM.It was found that the grain morphology prepared at different temperatures and times was not the same,and it could be kept dense within a certain range,but the overall continuity was not good and the compactness was poor.The resistivity and electrical conductivity of the film were tested by a four-probe resistance meter.It was found that the resistivity of the film decreased with the increase of heat treatment temperature and time,and the conductivity showed an upward trend.The CuFeS₂ film was prepared by using sulfate as raw material and chloride as raw material.It was found that the CuFeS₂ film prepared by using chloride as raw material has better crystallinity,the film is relatively uniform,and the resistivity of the chloride is much smaller than that of the sulfate,and the conductivity of the chloride is larger than that of the sulfate.（3）CuFeSe₂ powders and thin film materials were prepared by hydrothermal method and hydrothermal chemical co-reduction method.CuFeSe₂ powder material was prepared by hydrothermal method using raw material copper chloride,ferric chloride and selenium dioxide.It was found that when the temperature was 200℃and the time was 20 h,the target material had the best degree of crystallization and less impurities.The morphology of the material was studied and it was found that it consisted of block crystals with different shapes and sizes,and a small amount of agglomeration occurred.The CuFeSe₂ thin film material was prepared by hydrothermal chemical co-reduction method using copper chloride,ferric chloride and selenium dioxide.It was found that the CuFeSe₂ film had the best crystallinity when the temperature was200℃and the time was 30 h.The morphology of the film material at this temperature was tested.It was found that the film consisted of a lamellar crystal of about 10μm and a spherical crystal with a size of about 0.5μm,and the grain distribution was relatively uniform.The resistivity and electrical conductivity of the film were tested by a four-probe resistance meter.It was found that the resistivity and conductivity of the film did not change much with the change of the heat treatment conditions.